Flexible printing plate clamping device

ABSTRACT

A clamping device for thin flexible printing plates where the device has a plurality of first narrow width plate clamps for clamping the leading edge of a plate, a plurality of second narrow width plate clamps for clamping the trailing edge of the plate, and where the first and second clamps form cooperating pairs of clamps arranged in side-by-side longitudinal assembly in a small shallow axially extending groove on the surface of a plate cylinder of a rotary printing machine. Compression springs are positioned between the clamps of each pair of clamps and a leaf spring blade is held in place on each one of the second clamps by one of the compression springs. A longitudinally extending shaft is provided for each of the plurality of first clamps and of second clamps for opening and closing all of the clamps simultaneously.

United States Patent [191 Fusco FLEXIBLE PRINTING PLATE CLAMPING DEVICE [75] Inventor: Ralph L. Fusco, Commack, N.Y.

[73] Assignee: Wood Industries, Inc., Plainfield,

221 Filed: Apr. 26, 1971 211 Appl.No.:137,200

[ Aug. 14, 1973 Primary ExaminerRobert E. Pulfrey Assistant Examiner-William Pieprz Attorney-Pennie, Edmonds, Morton, Taylor & Adams ABSTRACT A clamping device for thin flexible printing plates where the device has a plurality of first narrow width plate clamps for clamping the leading edge of a plate, a plurality of second narrow width plate clamps for clamping the trailing edge of the plate, and where the first and second clamps form cooperating pairs of clamps arranged in side-by-side longitudinal assembly in a small shallow axially extending groove on the surface of a plate cylinder of a rotary printing machine. Compression springs are positioned between the clamps of each pair of clamps and a leaf spring blade is held in place on each one of the second clamps by one of the compression springs. A longitudinally extending shaft is provided for each of the plurality of first clamps and of second clamps for opening and closing all of the clamps simultaneously.

2 Claims, 4 Drawing Figures PAIENIED AUG 1 4 3 7 52 07 5 4 I INVENTOR Rol h Fusco ATTORNEYS FLEXIBLE PRINTING PLATE CLAMPING DEVICE BACKGROUND OF THE INVENTION The invention relates to clamping devices for printing plates on plate cylinders of printing machines and particularly to clamping devices for substantially thin, flexible plates.

Numerous clamping devices for thin, flexible printing plates have been developed, many of them combining other functions than clamping alone. The prior art mechanisms are complicated and expensive to manufacture, and maintenance and repair services of the devices have been involved, requiring major dismantling operations and extended downtime of the printing machine.

SUMMARY The clamping device according to the invention comprises basically a plurality of individual units which function independently from one another but which are operated in unison by one movement of either one or of two rotatable cam shafts extending longitudinally on both sides of the units. Each one of the units comprises one clamp for the leading edge of the printing plate and one clamp for the trailing edge of the plate, thetwo clamps arranged opposite to one another to form a pair of clamps. Two helical compression springs are located between the two clamps of a pair for urging the latter away from one another and for providing the back stroke against the movement caused by the cam shafts. The clamp for the trailing edge of the plate has a leaf spring blade thereon which is loosely hinged at its lower end and which is held against the inner side of the clamp by the force of one of the two compression springs abutting against the blade and held in place in an appropriate bore in the opposite, that is, the leading edge clamp. The entire structure of the unit requires little space, and therefore the longitudinally extending grooves milled in the surface of the plate cylinder into which the clamps are fitted are relatively small and shallow. This feature is highly desirable since any cutout of the plate cylinder body is minimized thus resulting in a stronger structure to provide a higher resistance against deflection in bending. Plate cylinders in printing machines run in bearings under considerable forces, therefore bending deflection of the cylinder body must be minimized to provide for a good quality of print in the center area of the cylinder.

The unit structure of a plate clamping device according to the invention lends itself to an economic mass production of the component parts of the clamping units. The unit structure also provides for easy interchangeability of the units for maintenance and repair purposes without taking the cylinder out of the printing machine and without major dismantling work on the cylinder which otherwise would cause an undesirable downtime of the machine. The basically simple structure of the clamping device provides a convenient, fast, plate changing operation, while at the same time providing a safe, accurate positioning and firm clamping of the printing plate to the cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the drawings which illustrate a preferred embodiment of the invention:

FIG. 1 is a cross-section of the clamping device according to the invention taken along the line 33 in FIG. 4, illustrating the trailing edge of a thin, flexible printing plate in the clamped position and the leading edge of the plate being in the unclamped position;

FIG. 2 is a cross-section of the clamping device of FIG. 1 illustrating the trailing edge of a thin, flexible printing plate in the unclamped position and the leading edge of the plate in the clamped position;

FIG. 3 is a cross-section of the clamping device of FIG. 1 with both the leading and the trailing edge of the thin, flexible printing plate shown in the clamped position; and

FIG. 4 is a longitudinal partly broken section of the clamping device of FIG. 1 taken along line 4-4 of FIG.

DESCRIPTION OF THE PREFERRED EMBODIEMNT Referring now in more detail to the drawings, there is shown in FIGS. 1, 2 and 3 a cross-section of the plate clamping device of this invention in three phases of operation. The plate cylinder 10 of a printing machine has one or more shallow grooves 11 machined in the surface thereof and extending longitudinally thereof. Clamping units 12 for the leading edge 13 and the trailing edge 14 of a thin, flexible printing plate 15 are located in the center portion 16 of grooves 11 in a sideby-side assembly (FIG. 4).,

Each one of clamping units 12 comprises a clamping part 17 for engaging a leading edge 13 of printing plate 15 and a clamping part 18 for engaging trailing edge 14 of printing plate 15 whereby the definition leading edge and trailing edge relates to the direction of rotation of plate cylinder 10, marked by the arrow R. Clamping part 17 comprises a piece of flat bar stock, the outside upper end 19 of which is slanted at the same angle as the face 20 of the cover bar 21 so that leading edge 13 of plate 15 which is accordingly bent can be clamped between face 20 and upper end 19. An upper bore 22 and a lower bore 23 are arranged on the inner side 24 of clamping part 17 for receiving therein two helical compression springs 25 and 26 respectively. A cam shaft 27 is rotatably held in a cut-out 28 of the cover bar 21 and against the bottom of groove 11. Cam shaft 27 extends longitudinally along the outside cam faces 29 of clamping parts 17 of all units 12 in center groove 16. By rotating cam shaft 27, the interaction between cam faces 29 and shaft 27 causes all clamping parts 17 of all units 12 to rock clockwise about the rounded heel end 30 of part 17, thereby opening the clamp so that bent edge 13 can be easily inserted therein (FIG. I) By the reverse rotation of shaft 27, clamping parts I7 rock counter-clockwise under the force of springs 25 and 26, thus firmly clamping the leading edge 13 between face 20 and outside upper end 19 (FIGS. 2 and 3).

Clamping part 18 for trailing edge 14 comprises a piece of flat bar stock having an upper end 31 slanted on the outside thereof conforming to the face 32 of the cover bar 33. The inside of upper end 31 is slightly bent and is slanted to provide a clamping face 34. A groove 35 is cut across the inner side 36 of part I8.'A leaf spring blade 37 is arranged in front of inner side 36, having a bent-off lower end 38 which fits loosely in groove 35 so that blade 37 can rock about lower end 38 in groove 35. Compression spring 25 abuts against spring blade 37 for hblding it in place, while compression spring 26 abuts against the lower end of clamping part 18. The upper end 39 of leaf spring blade 37 is slanted toward clamping face 34 of upper end 31 so that trailing edge 14 of printing plate 15 can be clamped therebetween. A pin 40 is riveted in the upper portion of spring blade 37, which reaches through a hole 41 near upper end 31 of clamping part 18 and is disposed to abut against the inner wall 42 of cover bar 33. A cam shaft 43, corresponding to cam shaft 27, is rotatably held in a cutout 44 in cover bar 33 and against the bottom of groove 11. Cam shaft 43 extends longitudinally of the outside cam faces 45 of clamping parts 18 of all units 12 in center groove 16. When cam shaft 43 is rotated, the interaction between cam face 45 of clamping part 18 and shaft 43 causes all clamping parts 18 of all units to rock clockwise about the rounded heel end 46 under the forces of both compression springs 25 and 26 until upper end 31 will come to rest with the outside face thereof I against face 32 of cover bar 33. Pin 40 abuts now against inner wall 42 of cover bar 33, holding leaf spring blade 37 back from clamping face 34. The clamp for trailing edge 14 of plate 15 is now open (FIG. 2) and the trailing edge of a new printing plate can be easily inserted. By the reverse rotation of shaft 43, clamping part 18 is rocked counterclockwise against the force of springs 25 and 26, the end of pin 40 moves away from wall 42 and trailing end 14 of plate 15 is now clamped between clamping face 34 and upper end 39 of leaf spring blade by the positive cam action of shaft 43 such that the clamp cannot open itself and is secured. In order to overcome slight differences of length of the printing plate, clamping part 18 as a whole can also be moved against the force of lower spring 26 by swinging clockwise about the clamping point of the plate bend which acts as a fixed point. (See FIGS. 1 and 3).

In order to secure units 12 in center groove 16, a block 47 is inserted at the end of groove 16 and is secured there by a screw 48. Units 12 can be easily slipped out with the help of a tool (not shown in the drawing) by removing block 47, when such action is required for servicing the mechanism or for maintenance purposes. Shafts 27 and 43 extend beyond block 47 into the space between the cylinder body and the bearer ring 49 and are axially secured by a block 50. Collars 51, 52 (collar 52 not visible in FIG. 4) are fastened at the ends of shafts 27, 43, respectively. Collars 51, 52 have a hole 53 into which a handle can be inserted for operating the mechanism by rotating the shafts.

It is seen that the plate clamping device as illustrated in the drawings comprises a minimum of easily machined parts and that because of its relatively simple construction, requires a minimum of space. This is a desirable feature as it allows a minimum of cutout of a plate cylinder to accommodate the parts, thus preserving the integrity of the plate cylinder.

I claim:

1. A printing plate clamping device for fastening a flexible printing plate having leading and trailing edges onto a plate cylinder of a printing machine wherein said plate cylinder has at least one longitudinally extending groove therein; said device comprising a plurality of first and second clamping means with each first clamping means being associated with a second clamping means to form a clamping unit positioned in said groove whereby together said plurality of first and second clamping means form a plurality of interchangeable units in said groove; each said first clamping means having a first substantially flat bar with a slanted upper edge adapted to engage the leading edge of a plate, a cam face on the outside thereof, a bore on the inside thereof, and a rounded heel on the lower edge thereof about which said first flat bar may rotate; each said second clamping means adapted to engage and clamp the trailing edge of a plate; compression spring means positioned in each said bore between each said firstand second clamping means to urge said clamping means apart; a first rotatable cam means in said groove positioned to the outside of all said units and engaging the cam faces of all the first flat bars; a second rotatable cam means in said groove positioned to the outside of all units and engaging all second clamping means whereby rotation of said first cam means in one direction will move said first clamping means towards said second clamping means to unclamp the leading edge of a plate and whereby rotation of said second cam means in one direction will move said second clamping means towards said first clamping means to clamp the leading edge of a plate; a first cover bar covering said first cam means having an inwardly slanting clamping face for engaging the leading edge of a plate; and a second cover bar covering said second cam means, said first and second cover bars together covering substantially all of said groove.

2. A printing plate clamping device for fastening a flexible printing plate having leading and trailing edges onto a plate cylinder of a printing machine wherein said plate cylinder has at least one longitudinally extending groove therein; said device comprising a plurality of first and second clamping means with each first clamping means being associated with a second clamping means to form a clamping unit positioned in said groove whereby together said plurality of first and second clamping means form a plurality of interchangeable units in said groove, each said first clamping means adapted to engage and clamp the leading edge of a plate; each said second clamping means having a second substantially flat bar with an inwardly slanted upper edge, a leaf spring blade having a slanting upper edge pivotally mounted with respect to the inside of said second flat bar with the inwardly slanted upper edge of said second bar and said leaf spring adapted to clamp a trailing edge of a plate between them, a cam face on the outside of said second bar, and a rounded heel on the lower edge of said second flat bar about which second flat bar may pivot; compression spring means positioned between each said first and second clamping means to urge said clamping means apart; a first rotatable cam means in said groove positioned to the outside of all said units and engaging all the first clamping means; a second rotatable cam means in said groove positioned to the outside of all units and engaging the cam faces of said second flat bars whereby rotation of said first cam means in one direction will move said first'clarnping means towards said second clamping means to unclamp the leading edge of a plate and wherebyv rotation of said second cam means in one direction will move said second clamping means towards said first clamping means to clamp the leading edge of a plate; a first cover bar covering said first cam means having an inwardly slanting clamping face for engaging the leading edge of a plate; and a second cover bar covering said second cam means having an inwardly slanting face for engaging said second bar, said first and second cover bars together covering substantially all of said groove.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION 3,752,075 Page 1 of 5 PATENT NO.

August 14, 1973 DATED INVENTOR(S) Ralph Fusco It is certified that'error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: Sheets 1 and 2 of the drawings should be deleted to insert the attached sheets therefor.

Signed and Scaled this In amy-third D a y of October 1979 [SEAL] finest:

LUTRELLE F. PARKER RUTH MASON Arresting Oflicer Acting Commissioner of Patents and Trademarks Page 2 of p PAIENIEU AUG I 41975 v 3 T52 075 

1. A printing plate clamping device for fastening a flexible printing plate having leading and trailing edges onto a plate cylinder of a printing machine wherein said plate cylinder has at least one longitudinally extending groove therein; said device comprising a plurality of first and second clamping means with each first clamping means being associated with a second clamping means to form a clamping unit positioned in said groove whereby together said plurality of first and second clamping means form a plurality of interchangeable units in said groove; each said first clamping means having a first substantially flat bar with a slanted upper edge adapted to engage the leading edge of a plate, a cam face on the outside thereof, a bore on the inside thereof, and a rounded heel on the lower edge thereof about which said first flat bar may rotate; each said second clamping means adapted to engage and clamp the trailing edge of a plate; compression spring means positioned in each said bore between each said first and second clamping means to urge said clamping means apart; a first rotatable cam means in said groove positioned to the outside of all said units and engaging the cam faces of all the first flat bars; a second rotatable cam means in said groove positioned to the outside of all units and engaging all second clamping means whereby rotation of said first cam means in one direction will move said first clamping means towards said second clamping means to unclamp the leading edge of a plate and whereby rotation of said second cam means in one direction will move said second clamping means towards said first clamping means to clamp the leading edge of a plate; a first cover bar covering said first cam means having an inwardly slanting clamping face for engaging the leading edge of a plate; and a second cover bar covering said second cam means, said first and second cover bars together covering substantially all of said groove.
 2. A printing plate clamping device for fastening a flexible printing plate having leading and trailing edges onto a plate cylinder of a printing machine wherein said plate cylinder has at least one longitudinally extending groove therein; said device comprising a plurality of first and second clamping means with each first clamping means being associated with a second clamping means to form a clamping unit positioned in said groove whereby together said plurality of first and second clamping means form a plurality of interchangeable units in said groove, each said first clamping means adapted to engage and clamp the leading edge of a plate; each said second clamping means having a second substantially flat bar with an inwardly slanted upper edge, a leaf spring blade having a slanting upper edge pivotally mounted with respect to the inside of said second flat bar with the inwardly slanted upper edge of said second bar and said leaf spring adapted to clamp a trailing edge of a plate between them, a cam face on the outside of said second bar, and a rounded heel on the lower edge of said second flat bar about which second flat bar may pivot; compression spring means positioned between each said first and second clamping means to urge said clamping means apart; a first rotatable cam means in said groove positioned to the outside of all said units and engaging all the first clamping means; a second rotatable cam means in said groove positioned to the outside of all units and engaging the cam faces of said second flat bars whereby rotation of said first cam means in one direction will move said first clamping means towards said second clamping means to unclamp the leading edge of a plate and whereby rotation of said second cam means in one direction will move said second clamping means towards said first clamping means to clamp the leading edge of a plate; a first cover bar covering said first cam means having an inwardly slanting clamping face for engaging the leading edge of a plate; and a second cover bar covering said second cam means having an inwardly slanting face for engaging said second bar, said first and second cover bars together covering substantially all of said groove. 